Pretreating uranium for metal plating



United States PRETREATING URANIUM FOR METAL PLATING Ralph F. Wehrmann, Waukegan, Ill., assignor to the United States of America as represented by the United States Atomic Energy Commission No Drawing. FiledMay 9, 1950, Ser. No. 161,020

2 Claims. (Cl. 204-1.5)

This invention deals with a process for pretreating uranium prior to applying metal coatings and the compositions suitable therefor.

Uranium is a highly reactive metal and oxidizes when process for treating uranium articles by which a very smooth surface is obtained.

Itis another object of this invention is process for treating uranium by which its surface is preconditioned so that a metal coating then applied is firmly bonded thereto.

to provide a I atent O Patented May 2, 1961 "ice , 'It is advantageous, though optional, mechanically to clean the uranium metal surface prior to the treatment by the process of this invention. This may be carried out by immersing the metal into a degreasing agent, such as trichloroethylene, and/or sandblasting the surface. For instance, sandblasting with 120 mesh steel grit for two to three minutes has been found satisfactory.

After the treatment with the oxalic acid-hydrochloric acid mixture, with or without the glycerine, the article is preferably rinsed by, or immersed into, a nitric acid solution; nitric acid obtained by diluting concentrated nitric acid with an equal amount of water and an immersion time of from one to ten minutes were found satisfactory for this purpose. Instead of, or in addition It is thus also an object of this invention to provide 1 These and other objects are accomplished by contacting the surface of the uranium articles with an aqueous mixture of polycarboxylic acid and hydrochloric acid. The concentrations of the acids can be varied widely.

' limited to the details given herein but that it may be The process of this invention can be carried out by simply immersing the article into ,the solution or else the article may be given an anodic treatment. While all kinds of polycarboxylic acids which are water-soluble,

" including oxalic, citric, malonic, tartaric, malic and g]uinvention, 1

taric acids, are suitable for the process of this oxalic acid is preferred.

The results of the process of this invention can still be further improved by adding glycerine to the carboxylic acid-hydrochloric acid aqueous mixture. Proportions of from 1 to'5% by weight of each, hydrochloric acid and glycerine are the optimal ranges.

results. Glycerine and hydrochloric acid can be added ever, this is not obligatory. Y

, The'process can be carried out at room temperature, i.e., at a temperature between 20 and 3 5 0,01 the solution can be heated to a temperature below is boiling fifteenminutes have been found suitable.

i When'thetreatment is carried out anodic'all'y, a cur- 7 rent density of-from 604,100amp'egres/ft. gives excellent I results. "In this case, the

temperature preferably ranges I A concentration of r v 10% with'regard to the oxalic acid has given excellent to the oxalic acid solution in about'equal amounts; how:

to, the nitric acid, the article may also be rinsed with water either of room temperature or of elevated temperature. I

In the following, an example is given of the process of this invention.

Uranium metal was immersed in a 10% aqueous solution of oxalic acid which contained 20 cc./liter each of glycerine and concentrated hydrochloric acid. The solution had a temperature of 40 C., and the article was immersed for thirty minutes. Thereafter, the thus treated article was immersed into nitric acid obtained by mixing commercial concentrated nitric acid with an equal volume of water for approximately ten minutes and rinsed with water. The thus pretreated article was then given a copper coating of a thickness of 1 mil by a conventional electrolytical method. The coating showed excellent adherence and had a very bright surface. The coated uranium article is suitable for use in a neutronic reactor of the type described in the copending application of Fermi et al., Serial No. 568,904, filed December .19, 1944, granted as US. Patent No. 2,708,656 on May 17, 1955.

It will be understood'that this invention is not to be comprising anodically treating a uranium article at a current density of from 60, to 100 amperes/ftfi. in an aqueous solution of about 10% polycarboxylic acid, from lto 5% by weight of glycerine. and from 1 to 5% by- 7 weight of'hydrochloric acid for from 30 seconds to 15 minutes, said solution having a temperature of from 20 to C.

2. The process of claim acid is oxalic acid. I I

References Citedin the file of this patent UNITED STATES PATENTS wherein the polycarboxylic 31,880 i Ely n; Apr. 2, 1861 1,011,203 Jahn Dec. 12, 1911 1,462,421 Pearson et al. July 17, 1923 1,495,538 Thews May 27, 1924 1,526,943 Thews Feb. 17, 1925 1,757,959 Gravel May 13, 1930 1,994,633 Boyd" 'Ma1. 19, 1935 2,287,050 'Miller ]'un e 23, 2,318,559 Percival f May 4,

7 2,465,987 ,Gorman Apr.-'5,-1949 1 FOREIGN PATENTS .1 16,548 Great Britain ...-1902 

1. A PROCESS FOR PRETREATING URANIUM FOR METAL PLATING, COMPRISING ANODICALLY TREATING A URANIUM ARTICLE AT A CURRENT DENSITY OF FROM 60 TO 100 AMPERES/FT2 IN AN AQUEOUS SOLUTION OF ABOUT 10% POLYCARBOXYLIC ACID, FROM 1 TO 5% BY WEIGHT OF GLYCERINE AND FROM 1 TO 5% BY WEIGHT OF HYDROCHLORIC ACID FOR FROM 30 SECONDS TO 15 MINUTES, SAID SOLUTION HAVING A TEMPERATURE OF FROM 20* TO 75* C. 